Injection device with an end of dose feedback mechanism

ABSTRACT

An injection device with a dose delivering mechanism being adapted to provide a non-visual, e.g. audible and/or tactile, feedback signal when a set dose has been at least substantially injected. A first and a second part of the injection device are adapted to perform a relative rotational movement with respect to each other. The relative rotational movement causes at least two parts of the injection device to abut or engage, and this abutment or engagement causes the non-visual feedback signal to be generated. A very distinct and precise feedback is provided as compared to prior art axial solutions because the generation of the feedback signal is initiated by the relative rotational movement. 
     Feedback signal may be generated by a change in a rotational velocity of at least one part, e.g. by changing the pitch of a threaded portion or by engaging a non-rotating part and a rotating part, thereby causing the non-rotating part to start rotating. May alternatively be generated by building up and releasing a tension. 
     The injection device is suitable for injecting insulin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/241,566,filed Aug. 19, 2016, which is a continuation of application Ser. No.11/813,389, filed Jul. 9, 2008 (issued as U.S. Pat. No. 9,457,154),which is a 35 U.S.C. § 371 national stage application of InternationalPatent Application PCT/EP2006/000486 (published as WO 2006/079481),filed Jan. 20, 2006, which claimed priority of European PatentApplication 05075187.4, filed Jan. 25, 2005; this application furtherclaims priority under 35 U.S.C. § 119 of U.S. Provisional Application60/647,491, filed Jan. 27, 2005; the contents of which are incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus for delivering liquiddrugs to a mammal, preferably a human being, preferably in asubcutaneous manner. More particularly, the present invention relates toan injection device which is capable of providing a non-visual feedbacksignal to a user indicating that a set dose has been injected by theinjection device.

BACKGROUND OF THE INVENTION

In the present disclosure reference is mainly made to the treatment ofdiabetes by injection of insulin. However, this is merely an exemplaryuse of the present invention. Thus, the present invention may be usedfor injection of any other suitable kind of drug, e.g. growth hormone.

Injection devices, e.g. in the form of injection pens, are mainly madefor users who have to inject themselves frequently, e.g. people havinginsulin-dependent diabetes or needing treatment by growth hormones. Anumber of requirements are set to such injection devices. The setting ofa dose must be easy and unambiguous and it must be easy to read the setdose. Furthermore, it must be possible, with a minimum of trouble, tocancel or change a wrongly set dose. Finally, when the dose is injectedthe dose setting mechanism must return to zero. This is very importantsince it ensures that the set dose is actually injected, therebyallowing the user to keep track of which dose is injected.

Many injection devices work with a threaded piston rod which cooperateswith a nut, the nut and the piston being capable of rotating relativelyto each other. The dose setting may be obtained by dialing the nut awayfrom a stop to which it is returned during injection by pressing thepiston rod forward, either manually or by means of a mechanically biasedmechanism, such as a spring, until the nut member abuts the stop. Inother injection devices one of the elements, the nut or the piston rod,is kept inrotatable while the other one is allowed to rotate a set angledepending on the set dose, whereby the piston rod is dialed a distancein a forward direction through the nut member.

In such prior art injection devices a dose is normally set by dialing adose setting member, and the set dose is injected by pushing aninjection button. In elongated pen shaped injection

devices the dose setting member and the injection button normally form asingle member. When the injection button is pushed the set dose isexpelled. However, the amount of drug expelled is only equal to the setdose if the injection button has been pushed as far as possible, thedose setting member thereby having been brought back to zero. In orderto ensure that the correct dose has actually been injected, the usertherefore has to visually inspect the position of the dose settingmember during the injection. This is disadvantageous because theinjection in some cases will take place in a part of the body wherevisual inspection during the injection is very difficult or evenimpossible. Furthermore, in case the user is visually impaired it may bedifficult for the user to visually inspect the dose setting memberduring or after the injection, regardless of where on the body theinjection is performed. Since it is not uncommon for people havingdiabetes to be visually impaired, this is an important aspect.

It is therefore desirable to provide a feedback signal to the userindicating that the set dose has been injected, the feedback signalbeing of a kind which makes it unnecessary for the user to visuallyinspect whether or not the set dose is injected.

Some prior art injection devices have a mechanism which informs the userthat a dose is being injected by producing an audible ‘click’ for eachdose unit being injected. However, since these clicks appear during theentire injection they do not provide a feedback signal indicating thatthe set dose has been injected, and the problem indicated above istherefore not solved by these injection devices. Prior art injectiondevices of this type are, e.g., described in U.S. Pat. No. 4,592,745, EP0 688 571 and US 2004/0210199.

In WO 98/57688 an injection device is disclosed which addresses theabove mentioned problem. Thus, WO 98/57688 discloses an injection devicehaving a dose setting device. A dose is set by dialing a dose settingmember. Apart from setting a dose the dialing action causes an injectionbutton to be moved from a position where it abuts a housing of theinjection device to a position where it protrudes from the housing. Theset dose is subsequently delivered by pushing the injection button backinto abutment with the housing.

In one embodiment a lock is activated when the injection button reachesthe housing, and the activation of the lock produces an audible clickindicating that the injection button is in abutment with the housing andthereby that the set dose has been delivered. During the injection,including the final part when the lock is activated, the injectionbutton is moved linearly. The linear distance travelled by the injectionbutton during the last few doses is relatively short. It may thereforebe difficult to determine accurately from the audible click produced bythe lock whether or not and when the set dose has been delivered.

EP 0 594 357 discloses another injection device which addresses theabove mentioned problem. Thus, EP 0 594 357 discloses an injectiondevice having a top section with resilient legs dependingperpendicularly from the top section. The outer surface of the resilientlegs has a ridge which rests on a ledge inside of the dose knob. Thedose knob may have an elongated section which fits into a cylindricalsleeve such that when the dose knob is pushed into the sleeve, at theend of injection, the top portion of the sleeve touches end of the legof the resilient legs displacing the ridge from the ledge and causing asnapping noise. As it is the case with the injection device described inWO 98/57688, the dose knob is moved linearly during injection, alsoduring the final part of the injection when the resilient legs aredisplaced from the ridge causing the snapping noise. Therefore theshortcomings described above are also applicable here.

SUMMARY OF THE INVENTION

It is, thus, an object of the present invention to provide an injectiondevice being capable of precisely and in a non-visual manner indicatingto a user when a set dose has been injected.

It is a further object of the present invention to provide an injectiondevice being capable of non-visually indicating to a user when a setdose has been injected, the indication being delivered to the user in avery distinct manner.

It is an even further object of the present invention to provide a dosedelivering mechanism for an injection device, the dose deliveringmechanism being capable of precisely and in a non-visual mannerindicating to a user when a set dose has been injected.

According to the present invention the above and other objects arefulfilled by providing an injection device comprising:

-   -   a housing,    -   a dose setting member being operable to set a desired dose to be        injected,    -   a piston rod being adapted to cooperate with a piston so as to        cause a set dose to be injected from an ampoule, and    -   a dose delivering mechanism being adapted to operate the piston        rod in such a way that a set dose is injected, the dose        delivering mechanism further being adapted to provide a        non-visual feedback signal to a user only at the end of        injection of a set dose, wherein first and second parts of the        injection device are adapted to perform a relative rotational        movement with respect to each other during injection of a dose,        and wherein said relative rotational movement causes at least        two parts of the injection device to abut or engage, said        abutment or engagement causing the non-visual feedback signal to        be generated.

The injection device of the present invention is very suitable for useby persons which have to frequently inject themselves, e.g. personshaving insulin-dependent diabetes or needing treatment by growthhormones. The desired dose being set by means of the dose setting memberis, thus, a dose of a specific drug which the person in question needsto inject at that specific point in time. The desired dose may be afixed dose which the person needs to inject each time an injection isperformed, or it may be a varying amount, e.g. varying according to thetime of day and/or one or more parameters which may be measured orchosen prior to setting the dose (e.g. blood glucose (BG) level,contents of a meal, etc.).

The piston rod is preferably adapted to push a piston into an ampoule,thereby causing the set dose to be injected. This may be obtained invarious ways and is well known and well described in the art.

The dose delivering mechanism is adapted to provide a non-visualfeedback signal to a user only at the end of injection of a set dose.Thus, the feedback signal may be generated when the set dose has beeninjected, e.g. exactly when or immediately after the last unit has beeninjected. Alternatively, the feedback signal may be generated before thecomplete dose has been delivered, e.g. when a few units remain to beinjected, the remaining units being injected while the feedback signalis sensed by the user. Thus, when the user perceives the feedback signalthe set dose will have been delivered, and the user will therefore notbe able to tell the difference between a feedback signal being generatedafter the dose has been completely injected and a feedback signal beinggenerated immediately before the dose has been completely injected. Inany event the user can regard the perception of the feedback signal asan indication that the set dose has been delivered, and the user maytherefore react correspondingly, e.g. by removing a pressure appliedmanually to an injection button.

Since the non-visual feedback signal is provided only at the end ofinjection of a set dose the user will know distinctly that when thefeedback signal is received the set dose has been fully injected. Thisis an advantage compared to prior art injection devices where a clickfor each injected dose unit is produced. In this case the user wouldhave to count the number of clicks produced and compare this to thenumber of set dose units in order to tell exactly when the set dose hasbeen fully injected.

A first part and a second part of the injection device are adapted toperform a relative rotational movement with respect to each other duringinjection of a dose. This may, e.g., be the housing and the piston rod,or it may be a separate member and any other part of the injectiondevice, e.g. the housing and/or the piston rod, the sole purpose of theseparate member being to generate the non-visual feedback signal. Threeor more parts of the injection device may perform mutual rotationalmovements during injection of a dose.

Furthermore, the relative rotational movement may be performed allthrough the injection of a dose or it may be performed during only partof the injection. Thus, the relative rotational movement may be startedor stopped at the end of injection of a set dose as defined above, inwhich case this starting or stopping may advantageously cause thenon-visual feedback signal to be generated.

The relative rotational movement causes at least two parts of theinjection device to abut or engage, and this abutment or engagementcauses the non-visual feedback signal to be generated. One or both ofthe parts which abut or engage may be the first and/or second parts,i.e. the parts performing the relative rotational movement.Alternatively, one or both of the parts which abut or engage may beother parts of the injection device. This will be described in furtherdetails below.

Due to the fact that the relative rotational movement initiates thegeneration of the non-visual feedback signal it is ensured that themovement generating the non-visual feedback signal is much longer than acorresponding movement in an injection device where the feedback signalis generated by a linear movement of one or more parts. Thereby thegenerated signal will be much more precise and distinct, and a far moreaccurate feedback signal has thereby been provided. This is veryadvantageous because it makes it much easier for the person to ascertainthat the expected and desired dose has actually been injected.

The non-visual feedback signal may comprise an audible and/or a tactilesignal. In this case the person using the injection device will be ableto hear and/or feel that the set dose has been injected. Alternativelyor additionally, the non-visual feedback signal may comprise any othersuitable kind of signal which can be perceived by other senses thansight. Furthermore, the non-visual feedback signal may be followed by avisual signal, e.g. a scale drum showing a ‘zero’, a lamp or a diodewhich is turned on or off or starts flashing simultaneously with thegeneration of the non-visual feedback signal. Thereby the user may, inaddition to the non-visual feedback signal, use this visual feedbacksignal to further ensure that the set dose has actually been injected.

In one embodiment of the present invention the abutment or engagement iscaused by a change in a rotational velocity of at least one part of thedose delivering mechanism. This may, e.g., be accomplished by allowing aseparate member to start rotating at the end of injection of a set dose,typically in such a way that this member rotates during injection of thelast few units of the set dose. The rotation of this separate memberwill in turn generate a non-visual feedback signal to the user. Thus, inthis case the rotational velocity of this member relatively to, e.g.,the housing, changes from zero to a certain velocity, and this changecauses the non-visual feedback signal to be generated, e.g. in the formof a clicking sound generated by protruding parts present on theseparate member moving against an inner part of the housing or an outerpart of the piston rod.

Alternatively or additionally, the change in rotational velocity maycause a tactile feedback signal to be generated. It may, e.g., bepossible to feel the rotational movement itself, and thereby it may bepossible for the user to detect a substantial change (decrease orincrease) in the rotational velocity.

In one embodiment the injection device may further comprise a ratchetoperating the piston rod and having a threaded portion being adapted toengage with a part of the dose delivering mechanism, in which case thechange in a rotational velocity is generated by a change in the pitch ofthe threaded portion of the ratchet, said change in the pitch in returncausing a change in a translational velocity of said part of the dosedelivering mechanism, said change in translational velocity causing atleast two parts of the injection device to abut, thereby causing thenon-visual feedback signal to be generated.

In this embodiment the non-visual feedback signal preferably comprises atactile feedback signal. Thus, the part of the dose delivering mechanismwhich is adapted to engage with the threaded portion of the ratchet ispreferably in directly or indirectly contact with the user duringinjection of a dose. Thus, the part may be, form part of or beoperatively connected to an injection button which the user pressesduring injection. Thereby the user will be able to feel the change intranslational velocity.

The pitch may be changed from a certain value used during the main partof the injection to zero, i.e. the threaded portion simply stops at aposition corresponding to the end of injection of a set dose. In thiscase the user will feel a kind of ‘axial resistance’ during theinjection until the ratchet/dose delivery part reaches the positionwhere the threaded portion stops. Then the part will stop rotating andinstead increase the velocity of a translational (axial) movement whichis also performed while the ratchet/dose delivery part travels thethreaded portion, due to the pitch of the threaded portion. The userwill be able to feel this increase in translational velocity.Furthermore, the translational movement is preferably eventuallystopped, e.g. due to part of the dose delivery mechanism abutting a stopmember. This stop will also be very distinctly felt by the user, therebyproducing a non-visual feedback signal, and it may further produce asound, in which case the non-visual feedback signal comprises a

tactile as well as an audible signal. In this embodiment the two partsof the injection device which are caused to abut may advantageously be ascale drum and a part of the housing, the scale drum performing arotational and axial movement defined by the threaded portion.

Alternatively, the two parts may be a dose knob and a proximal part ofthe housing, the dose knob performing an axial movement which followsthe axial part of the movement of the scale drum as described above.

Alternatively, the pitch may either increase or decrease from onenon-zero value to another. This has the advantage that the engaging partis readily moved back into engagement with the threaded portion when anew dose is to be set.

In another embodiment the dose delivering mechanism may comprise a firstdose part and a second dose part, the first dose part being adapted torotate relatively to the housing during injection of a dose and thefirst dose part comprising means for engaging the second dose part atthe end of injection of a set dose, thereby causing the second dose partto rotate along with the first dose part, in which case the non-visualfeedback signal is generated by the resulting rotational movement of thesecond dose part.

In this embodiment the rotational movement of the second dose partincreases from zero to a non-zero value at the end of injection of theset dose. The second dose part may be provided with teeth, protrusions,flexible arms or similar means being adapted to be moved against anotherpart of the device during rotation of the second dose part, therebyproducing a sound which at least partly constitutes the non-visualfeedback signal.

The second dose part may be positioned between the first dose part andthe housing. In case the second dose part is provided with teeth,protrusions, flexible arms or the like as described above, these mayadvantageously be moved against a part of the housing when the seconddose part is rotated along with the first dose part.

Alternatively, the non-visual feedback signal may be generated as aresult of an abutment between two parts of the dose delivering mechanismperforming a relative rotational movement. The feedback signal may,e.g., be obtained by releasing a tension which has previously beenintroduced in a part of the injection device, the release of the tensionbeing caused by the abutment between the two parts.

The tensed part may comprise a spring means, such as a separate springmember or at least one resilient portion of at least one of the firstand second parts performing the relative rotational movement. In casethe spring means is in the form of at least one resilient portion of thepart(s) the non-visual feedback signal may be generated in the followingmanner. First the resilient portion(s) is/are bent into a tensedposition. At a later time this tension is released, e.g. by rotating theresilient portion(s) away from a part which holds the resilientportion(s) in the tensed position. Thereby the resilient portion(s) willrestore its/their relaxed position(s), and this movement will generate aclicking sound, i.e. a non-visual feedback signal. The resilientportion(s) may be in the form of spring arm(s), in which case a soundmay be generated due to moving air caused by sudden release of thetensed spring arm(s). Alternatively, abutment between a moving part anda release mechanism may release the tension of the resilient portion(s).

The tension may be introduced during dose setting, e.g. by tightening aspring member or moving a resilient portion into a tensed position asdescribed above. This may be obtained by letting the dose settingmechanism be connected to a spring member, e.g. in such a way that aspring is tightened when a dose setting member is turned, or in such away that a part being provided with a resilient portion is rotated alongwith a dose setting member, thereby causing the resilient part to bemoved into a tensed position.

Alternatively, the tension may be introduced during injection of a dose.This may be obtained in a manner very similar to what is describedabove. However, in this case the tensed part should be operativelyconnected to the dose delivering mechanism.

The dose delivering mechanism may be adapted to be manually operated,e.g. by means of an injection button which the user must press manuallyduring the injection.

Alternatively, the dose delivering mechanism may be adapted to beoperated by means of a mechanically biased mechanism, e.g. comprising atleast one spring. The mechanically biased mechanism may, in this case,be biased during setting of a dose. When the injection is subsequentlyperformed this is done by releasing the tension previously built up inthe mechanically biased mechanism, and the stored energy will then causethe set dose to be injected. This kind of injection device does notrequire a force applied by the user in order to inject a set dose.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described with reference to theaccompanying drawings in which:

FIG. 1 shows a cross section through an injection device according to afirst embodiment of the invention and being in a position where a dosehas been set,

FIG. 2 shows a cross section through the injection device of FIG. 1 in aposition where a dose has been injected,

FIG. 3 shows a click item adapted to be positioned in the injectiondevice of FIGS. 1 and 2,

FIG. 4 shows a threaded inner part being adapted to be positioned in aninjection device according to a second embodiment of the invention,

FIG. 5 shows a top view of an outer part being adapted to engage withthe inner part of FIG. 4,

FIG. 6 is a cross section along line A-A in FIG. 5,

FIGS. 7-10 show parts of injection devices according to a third, fourth,fifth and sixth embodiment of the invention, respectively, all having aspring arm and a wedge structure,

FIG. 11 shows part of an injection device according to a seventhembodiment of the invention having a spring arm and a release mechanism,

FIG. 12 shows an outer part of the injection device of FIG. 11 from adifferent angle, and

FIGS. 13-15 show part of an injection device according to an eighthembodiment of the invention having a spring arm, at various points intime.

The Figures are schematic and simplified for clarity, and they only showdetails which are essential to the understanding of the invention whileother details are left out. Throughout the description of the drawingsthe same reference numerals will be used for identical or correspondingparts.

DETAILED DESCRIPTION OF THE DRAWINGS

When in the following terms as ‘upper’ and ‘lower’, ‘left’ and ‘right’,‘horizontal’ and ‘vertical’, ‘clockwise’ and ‘counter clockwise’ orsimilar relative expressions are used, these only refer to theaccompanying drawings and not to the actual situation of use. The shownFigures are schematic representations for which reason the configurationof the different structures as well as their relative dimensions areintended to serve illustrative purposes only. In that context it may beconvenient to define that the term ‘distal end’ in the accompanyingdrawings is meant to refer to the end of the injection device carryingan injection needle, whereas the term ‘proximal end’ is meant to referto the opposite end pointing away from the injection needle.

FIG. 1 shows a cross section through an injection device 1 according toa first embodiment of the invention. At its distal end the injectiondevice 1 is provided with a portion 2 being adapted to carry aninjection needle (not shown). At its proximal end the injection device 1comprises a combined dose setting and injection button 3. During dosesetting the dose setting and injection button 3 is rotated. This causesthe dose setting and injection button 3 to be moved away from a housing4 to the position shown in FIG. 1. During injection the user presses thedose setting and injection button 3, thereby moving it back into thehousing 4.

This movement causes the set dose to be injected from the injectiondevice 1. Inside the dose setting and injection button 3 there ispositioned a click item 5 which is provided with a set of teeth 6 beingadapted to engage with a corresponding tooth 7 positioned on a ratchet8. During injection the ratchet 8 will rotate relatively to the housing4 while the click item 5 will not rotate.

FIG. 2 shows a cross section of the injection device 1 of FIG. 1.However, in FIG. 2 a dose has just been injected, i.e. the dose settingand injection button 3 has been pushed to a position inside the housing4. Thereby the set of teeth 6 on the click item 5 engage with the tooth7 on the ratchet 8. Since the ratchet 8 rotates during the injection,this will cause the click item 5 to be rotated along with the ratchet 8.This rotational movement will cause the click item 5 to produce a soundin a manner which will be explained further below with reference to FIG.3. Since the click item 5 is only rotated during the injection of thelast few units of the set dose the produced sound indicates that the setdose has been substantially injected. Thereby a non-visual feedbacksignal has been generated.

FIG. 3 is a perspective view of a click item 5 adapted to be inserted inthe injection device 1 of FIGS. 1 and 2. The part of the click item 5positioned opposite the set of teeth 6 is provided with two resilientparts 9. The resilient parts 9 are resilient due to a reduced thicknessof the material making up the parts 9 as compared to the thickness ofthe material making up the remaining parts of the click item 5. When theclick item 5 is rotated as described above the resilient parts 9 will bemoved against the inner part of the housing 4, and this will cause theresilient parts 9 to be alternatingly tensed and released. Each time theresilient parts 9 are released they will produce a clicking sound,thereby generating the non-visual feedback signal.

FIG. 4 shows a threaded inner part 10 being adapted to be insertedinside a housing of an injection device according to a second embodimentof the invention. The main part of the thread 11 has a constant pitch.However, in the lower part of the thread 12 the pitch is abruptlydecreased. This can be seen in the form of an axial edge 13. Thereby apart engaging with the thread 11, 12 will be moved abruptly relativelyto the inner part 10 along an axial direction when the engaging partreaches the lower part of the thread 12, i.e. when it reaches the axialedge 13. This abrupt movement, and not the least the following abruptstop when this movement stops, can be felt by the user as will bedescribed below. Furthermore, the location of the axial edge 13 towardsthe end of the threaded portion 12 ensures that the felt abrupt movementindicates the end of injection of a set dose. Thereby a non-visual(tactile) feedback signal has been provided as a result of a change inthe pitch of a threaded portion 11, 12.

FIG. 5 shows a top view of an outer part 14 being adapted to bepositioned around the threaded inner part 10 of FIG. 4. The outer part14 is provided with two protruding parts 15 each being adapted to engagewith the thread 11, 12 of the inner part 10.

FIG. 6 shows a cross section through the outer part 14 shown in FIG. 5along the line A-A. During injection of a dose the inner part 10 and theouter part 14 will initially be relatively positioned in such a way thatthe protruding parts 15 engage with the part of the thread 11 beingpositioned opposite the lower part of the thread 12. The outer part 14is then pushed inwards, thereby allowing the protruding parts 15 totravel the threaded portion 11. Due to the thread 11 the inner part 10and the outer part 14 perform a relative rotational movement. When theprotruding parts 15 reach the axial edge 13 the axial velocity of theouter part 14 will increase abruptly as described above, and because theuser is manually pressing the outer part 14 this abrupt movement, aswell as the abrupt stop occurring when the outer part 14 abuts a stopmember 16 present on the inner threaded part 10 (see FIG. 4), will befelt by the user. Thereby a tactile feedback signal is provided.Furthermore, the outer part 14 abruptly abutting the stop member 16 mayproduce a sound, thereby providing an audible feedback signal inaddition to the tactile feedback signal.

FIG. 7 shows part of an injection device according to a third embodimentof the invention. The Figure shows an inner part 10 and an outer part14. The inner part 10 and the outer part 14 are adapted to be rotatedrelatively to each other during injection. The outer part 14 is providedwith a wedge structure 17 and the inner part 10 is provided with aspring arm 18. During injection, in addition to the mutual rotation, theinner part 10 is moved in an axial direction indicated by the arrow.When the spring arm 18 reaches the wedge structure 17 a protruding part19 of the spring arm 18 will engage an upper part 20 of the wedgestructure 17. This will cause the spring arm 18 to be pressed in adirection opposite to the one indicated by the arrow, therebyintroducing a tension in the spring arm 18. The tension is, thus, builtup during injection. The protruding part 19 will subsequently be movedalong the upper part 20 of the wedge structure 17 until it reaches theend 21 of the wedge structure 17. The protruding part 19 will then ‘fallover the edge’ to the position shown in FIG. 7, thereby releasing thetension which was previously built up in the spring arm 18. This suddenrelease of the tension produces a sound due to air being moved by thespring arm 18 and/or due to the protruding part 19 hitting a stationarypart of the outer part 14. Thereby an audible feedback signal has beenproduced, and by positioning the wedge structure 17 in an appropriatemanner, the feedback signal will indicate to the user that the set dosehas been injected.

When a new dose is to be set, the protruding part 19 will pass the wedgestructure 17 via a tapered part 22 on the wedge structure 17.

FIG. 8 shows part of an injection device according to a fourthembodiment of the invention. The fourth embodiment is very similar tothe third embodiment shown in FIG. 7. FIG. 8 also shows an inner part 10having a spring arm 18 and an outer part 14 having a wedge structure 17,the inner part 10 and the outer part 14 being adapted to rotate inrelation to each other during injection. The spring arm is provided witha protruding part 19. During injection the inner part 10 movesrelatively to the outer part 14 in a direction indicated by the arrow.When the spring arm reaches the wedge structure 17 the protruding part19 will be caught in a track 23 and moved along this track 23. Due tothe geometry of the wedge structure 17 this movement will result in thespring arm 18 being pressed in a direction away from the outer part 14,thereby introducing a tension in the spring arm 18. Thus, the tension isbuilt up during the injection. When the protruding part 19 reaches theend 21 of the wedge structure 17 it will ‘fall over the edge’, therebyreleasing the tension which was previously built up in the spring arm18. This will result in an audible feedback signal being generated asdescribed above.

When a new dose is to be set, the protruding part 19 will pass the wedgestructure 17 by being lifted in an axial direction along the end 21 ofthe wedge structure 17.

FIG. 9 shows part of an injection device according to a fifth embodimentof the invention. FIG. 9 shows an inner part 10 having a spring arm 18and an outer part 14 having a wedge structure 17. During injection theinner part 10 will move relatively to the outer part 14 in a directionindicated by the arrow. However, in this embodiment the inner part 10and the outer part 14 do not rotate relatively to each other. Insteadthe injection device comprises a rotational part 24 which rotates duringinjection relatively to the inner part 10 and the outer part 14. Whenthe spring arm 18 reaches the wedge structure 17 it will be pushed in adirection away from the outer part 14 and towards the rotational part24. Thereby it is moved into a path of a protruding part 25 on therotating part 24. When the protruding part 25 is rotated to the positionof the spring arm 18, it will therefore push the spring arm 18 out ofits path again, thereby introducing a tension in the spring arm 18. Whenthe protruding part 25 has passed the position of the spring arm 18, thespring arm 18 will again be free to move into the path of the protrudingpart 25, thereby releasing the tension which was previously built up inthe spring arm 18. Thereby an audible feedback signal is generated dueto air being moved be the spring arm 18 and/or due to the spring arm 18hitting a wall of the rotational part 24, as described above.

FIG. 10 shows part of an injection device according to a sixthembodiment of the invention. The Figure shows an inner part 10 having aspring arm 18 and an outer part 14 having a wedge structure 17. Theinner part 10 and the outer part 14 are adapted to rotate relatively toeach other during injection. Furthermore, the inner part 10 movesrelatively to the outer part 14 in the direction indicated by the arrowduring injection. When the spring arm 18 reaches the wedge structure 17it will be caught by one of the wedges. Due to the geometry of the wedgestructure 17 and to the continued rotational and axial movement (in thedirection of the arrow) of the inner part 10, the spring arm 18 will bepressed in a direction opposite the direction indicated by the arrow,thereby introducing a tension in the spring arm 18. Subsequently whenthe spring arm 18 reaches the end 21 of the wedge it will ‘fall over theedge’, thereby releasing the previously built up tension. This willcause an audible feedback signal to be generated as described above.

FIG. 11 shows part of an injection device according to a seventhembodiment of the invention. The Figure shows an inner part 10 having awedge structure 17 and an outer part 14 having a spring arm 18 and alocking mechanism (not shown in FIG. 11). The inner part 10 and theouter part 14 are adapted to rotate in relation to each other duringsetting of a dose and during injection. The inner part 10 is typically ascale drum or is adapted to rotate along with a scale drum duringsetting of a dose and during injection. Thus, when a dose is set theinner part 10 is rotated in such a way that the wedge structure 17presses the spring arm 18 outwards and into engagement with the lockingmechanism, thereby introducing a tension in the spring arm 18. Thus, inthis embodiment the tension is introduced during setting of the dose.The locking mechanism will maintain the spring arm 18 in the tensedposition during the remaining setting of the dose and during the mainpart of the injection.

However, when the inner part 10 is returning to the initial position arelease mechanism 26 on the wedge structure 17 releases the lockingmechanism, thereby releasing the tension which was previously built upin the spring arm 18. Thereby an audible signal is generated asdescribed above, and because the locking mechanism is released when theinner part 10 is returning to the initial position, this audible signalindicates that the set dose has been injected.

FIG. 12 shows the outer part 14 of the injection device of FIG. 11. Theouter part 14 has a locking mechanism 27 which is in a locking position,i.e. it engages the spring arm 18. Thus, in FIG. 12 the spring arm 18 istensed. When the inner part (not shown) approaches the outer part 14 asdescribed above, the release mechanism (not shown) will push the lockingmechanism 27 downwards, and the tensed spring arm 18 will then restoreits relaxed position, i.e. it will move towards the centre of the outerpart 14. Thereby the tension built up in the spring arm 18 is suddenlyreleased.

FIG. 13 shows part of an injection device 1 comprising a scale drum 28and a spring arm member 29 positioned at the proximal end of theinjection device 1. The spring arm member 29 is provided with a springarm 18 which may be deflected in a proximal direction, i.e. away fromthe scale drum 28.

During injection of a set dose, the scale drum 28 performs a rotationalmovement as well as an axial movement towards the spring arm member 29.This movement will eventually cause an upper portion 30 of the scaledrum to abut a protrusion 31 of the spring arm 18. As the scale drum 28continues the rotational and axial movement, the spring arm 18 isdeflected in a proximal direction, thereby causing a tension to be builtup in the spring arm 18.

FIG. 13 shows a situation where the upper portion 30 of the scale drum29 and the protrusion 31 of the spring arm 18 abut, and a tension hasstarted to build up in the spring arm 18.

FIG. 14 shows the injection device of FIG. 13. In FIG. 14 a tension hasbeen built up in the spring arm 18 as described above. The protrusion 31of the spring arm 18 is positioned very near a recess 32 formed in thescale drum 28. Thus, further rotation of the scale drum 28 will causethe protrusion 31 to ‘fall over the edge’ into the recess 32. Therebythe tension which has previously been built up in the spring arm 18 isreleased, and an audible feedback signal is generated by vibrating airand/or by the protrusion 31 hitting a lower edge of the recess 32.

This situation is illustrated in FIG. 15, showing the injection device 1of FIGS. 13 and 14 in a situation where the tension previously built upin the spring arm 18 has been released as described above.

When a new dose is to be set, the feedback mechanism needs to be resetin order to be able to provide an audible feedback signal when thesubsequent dose has been injected. This is done by leading theprotrusion 31 of the spring arm 18 via a path or track (not visible inFIGS. 13-15) positioned behind the upper portion 30 of the scale drum 28during the next dose setting. When the set dose is sufficiently large,the scale drum 28 and the spring arm member 29 will be sufficientlyspaced apart to allow the protrusion 31 to be positioned above the upperpart 30 of the scale drum 28. Thereby the feedback mechanism has beenreset, i.e. the spring arm 18 is once again ready for being deflected ina proximal direction as described above.

The injection device shown in FIGS. 13-15 is particularly suitable forhaving a dose delivering mechanism which is adapted to be operated bymeans of a mechanically biased mechanism, such as a spring.

Some preferred embodiments have been shown in the foregoing, but itshould be stressed that the invention is not limited to these, but maybe embodied in other ways within the subject matter defined in thefollowing claims.

The invention claimed is:
 1. An injection device comprising: a housinghaving a longitudinal axis, a dose setting member being operable by auser to set a desired dose of a varying amount to be injected, thedesired dose thereby being a set dose, a piston rod being adapted tocooperate with a piston so as to cause a set dose to be injected from anampoule, and a dose delivering mechanism being adapted to operate thepiston rod in such a way that the set dose is injected by a mechanicallybiased mechanism comprising at least one spring and wherein theinjection is subsequently performed by releasing the stored energypreviously built up in the mechanically biased mechanism and whichstored energy will cause the set dose to be injected, the dosedelivering mechanism further being adapted to provide an audiblefeedback signal to a user only at the end of injection of the set dose,wherein first and second parts of the injection device are adapted toperform a relative rotational movement around a longitudinal axis withrespect to each other during injection of the set dose, and wherein saidrelative rotational movement causes at least the first part and thesecond part of the injection device to abut or engage, said abutment orengagement causing the audible feedback signal to be generated, whereinthe audible feedback signal is generated as the first part and thesecond part of the dose delivering mechanism performing said relativerotational movement are moved against each other, and the audiblefeedback signal is generated by releasing a tension which has previouslybeen introduced in a part of the injection device comprising at leastone resilient portion of at least one of the first part and the secondpart performing said relative rotational movement.
 2. The injectiondevice according to claim 1, wherein the abutment or engagement iscaused by a change in a rotational velocity of at least one part of thedose delivering mechanism.
 3. The injection device according to claim 2,further comprising a ratchet operating the piston rod and having athreaded portion being adapted to engage with a part of the dosedelivering mechanism, and wherein the change in a rotational velocity isgenerated by a change in the pitch of the threaded portion of theratchet, said change in the pitch in return causing a change in atranslational velocity of said part of the dose delivering mechanism,said change in translational velocity causing at least two parts of theinjection device to abut, thereby causing the audible feedback signal tobe generated.
 4. The injection device according to claim 2, wherein thedose delivering mechanism comprises a first dose part and a second dosepart, the first dose part being adapted to rotate relatively to thehousing during injection of a dose and the first dose part comprisingstructure for engaging the second dose part at the end of injection of aset dose, thereby causing the second dose part to rotate along with thefirst dose part, and wherein the audible feedback signal is generated bythe resulting rotational movement of the second dose part.
 5. Theinjection device according to claim 4, wherein the second dose part ispositioned between the first dose part and the housing.
 6. The injectiondevice according to claim 1, wherein the at least one resilient portionis a spring arm.
 7. The injection device according to claim 6, whereinthe tension is introduced during dose setting.
 8. The injection deviceaccording to claim 1, wherein the tension is introduced during dosesetting.
 9. The injection device according to claim 1, wherein thetension is introduced during injection of a dose.